Improvement in molds for forming artificial grindstones



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I '6. HART. Mold for forming Artificial Grind-Stones.

No, 167 527 Patented Sept. 7,1875.

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W OMQW NITED STATEs GILBERT HART, OF DETROIT, MICHIGAN.

IMPROVEMENT IN MOLDS FOR FORMlNG ARTIFICIAL GRINDSTONES.

Specification forming part of Letters Patent No. 167,527, datedSeptember 7, 1875; application filed March 13, 1875.

To all whom it may concern Be it known that I, GILBERT HART, of Detroit,in the county of Wayne and in the State of Michigan, have inventedcertain new and useful Improvements in Molds for Forming ArtificialGrindstones; and do hereby declare that the following is a full, clear,and exact description thereof, reference being had to the accompaningdrawing, making a part of this specification, in which- Figure 1 is aperspective View of the exterior of my improved mold. Fig. 2 is avertical central section of the same; and Fig. 3 is a like view, showinga modification in the construction of the lower portion of said mold.

Letters of like name and kind refer to like parts in each of thefigures.

My invention has for its object an increase in the facility and accuracyof construction of artificial grindstones, emery-wheels, 85c. and itconsists, principally, in the employment, within a mold, of a detachablelining of thin metal, paper, or other like material, which may beremoved with the molded article, substantially as and for the purposehereinafter specified. It consists, further, in the construction of thesectional mold employed, substantially as and for the purposehereinafter shown. 7

In the annexed drawing, A represents the base or bottom of my mold,which is constructed, preferably, from cast metal, is circular ingeneral form, and is provided upon its upper side with an annularflange. B, which in diameter and height corresponds to thediameter andthickness of the stone or wheel to be molded. The flange B may be castwith, and form part of, the bottom plate A, as shown in Fig. 2 or, asseen in Fig. 3, said flange may be formed separate, and, at its loweredge and outer side, fit within a shoulder, a, provided upon said plate.Upon the upper edge of the flange B is fitted a cover, 0, which is plainupon its sides, and, in plan view, has substantially the same shape anddimensions as the bottom plate A. Two" or more bolts D and D passvertically through the portionsof said bottom plate and cover outside ofsaid flange B, and enable the whole to be closely confined together whendesired. At the axial centers of the plate A and cover 0 are providedopenings a and a, respectively, within which is fitted a round pin, E,that corresponds in size to the dimensions of the mandrel-opening thatis to be formed at the center of the stone or wheel to be molded. Theopening to within the plate a is somewhat smaller than the body of thepin E, and the lowerend of the latter is correspondingly reduced so asto fit therein, a shoulder c, at the upper end of such reduced portionbeing in contact with the upper side of said plate. The projecting endof said pin is threaded, and upon the same is placed a nut, E, which,when screwed upward to place, confines said pin firmly in position.

The mold thus constructed is used by removing the cover, filling theinterior space with plastic material for forming the artificial stone,and then replacing and securing said cover in position, after which saidmold is set aside until its contents dry or harden. When the moldedmaterial has become sufficiently set, the cover is removed, thecenter-pin loosened, and the same, with the stone, is then removed fromthe mold; but, as the plastic material employed for such purposesexpands in drying, it has heretofore been found-necessary to give .acertain amount of flare or draft to the mold, in order that thecompleted article might be withdrawn therefrom without mutilation.

This method of facilitating the .removal of the stone is, however, opento the objection that the amount of draft requisite in order to overcomeits tendency to adhere to the sides of the mold gives to the peripheryof said stone unequal dimensions at its edges, and renders the articleproduced less useful than would be the case were said periphery formedupon a line parallel to its axis. To overcome this objection I fitloosely within my mold a detachable lining, F, made, preferably, of thinsheet F metal, although hard paper or other similar 5 substance can beemployed for this p rpose,

if desired, The lining F may either be constructed in two sections, asin the mold shown in Fig. 2, or in three sections, as shown in Fig. 3but in either case its interior faces receive the plastic material, andit is removed from the mold with the same when properly set, after whichthe detachment of said lining is easily and quickly efl'ected. V

By my method the molded stones are easily and quickly removed from themold, and when separated from the lining have perfect accuracy of form.

When the annular flange B is constructed separate from the bottom plateAit is divided vertically at one point, and is removed with the moldedarticle, after which it may be easily sprung open, so as to release saidarticle.

Having thus fully set forth the nature and merits of my invention, whatI claim as new 1s 1. In combination with the mold A, B, and

have hereunto set my hand this 6th day of March, 1875.

GILBERT HART. Witnesses:

GEORGE Sco'rT, G. L. HOWARD.

